The present invention relates generally to a foldable information processing apparatus, such as a cell phone (including a personal digital cellular (“PDC”), a personal handy phone system (“PHS”), and another mobile communication terminal, which are generally referred to as “mobile radio communication apparatuses”), and more particularly to an internal structure of its hinge part.
Along with recent widespread of the mobile radio communication apparatuses, various demands have been made on them including an improved operability and durability of each component, and a smaller housing.
In general, the cell phone is classified into a foldable cell phone and a rod-type cell phone. Among them, the foldable cell phone typically has a movable-side housing with a liquid crystal display (“LCD” hereinafter) screen and a fixed-side housing with a ten-key, and make them foldable through a hinge part. A connector passes through the hinge part in the foldable cell phone between the movable-side housing and the fixed-side housing, and electrically connects the movable-side housing to the fixed-side housing to each other. In general, the connector is made of a cable line and a flexible printed circuit board (“FPC” hereinafter) between substrates. The cable includes, for example, a coaxial cable used to transmit a high-frequency signal. The FPC is used, for example, to connect both printed boards of the movable-side housing and fixed-side housing to each other, and transmit various signals between these printed boards.
The FPC is classified into a curl-type structure in which the FPC is curled once in the hinge part, and a crank-type structure in which the FPC is twisted and bent in the hinge part. Although the curl-type structure is the current mainstream, the crank-type structure enables the external form of the hinge part to be smaller than the curl-type structure. Therefore, the future demand of the crank-type structure is expected since it contributes to the miniaturization of the cell phone.
Prior art includes, for example, Japanese Patent Applications, Publication Nos. 2004-7218 and 2003-198155.
In the foldable cell phone, a path for the FPC when the movable-side housing opens is longer than that when the movable-side housing closes. Since the FPC's path length is thus different between the opening and closing states of the movable-side housing, the FPC is pulled too tight to close, torn or stretched out so that its internal circuit is broken, if the FPC's length is set to the path length in the opening state of the movable-side housing. Thus, the FPC's length should be set based on the path length in the closing state of the movable-side housing. As a result, the FPC has an extra length to the path length of the opening state of the movable-side housing.
However, due to this extra length, the FPC's end surface is pressed against the internal surface of the hinge part when the movable-side housing is opened and closed, generating the rustle of frictional noises, and lowering the operability or operational comfort. The substrate of the FPC is made generally of resin, such as polyimide. On the other hand, the hinge part is made of a hard metal material, such as zinc and SUS sintered member so as to protect the connector and stabilize the joint between the fixed-side housing and the movable-side housing. Therefore, when the FPC and hinge part rub against each other, the FPC's end surface wears away. As the FPC's wear advances, the FPC's signal line exposes and breaks down, consequently lowering the durability of the foldable cell phone.